Piston



Sept. 26, 1939. L. A. HALLSTEAD PISTON lim Filed Nov; 16, 1938 Patented Sept. 26, 1939 UNITED STATES PATENT OFFICE PISTON Leon A. Hallstead, Grand Island, N. Y.

Application November 16, 1938, Serial No. 240,832

4 claims4 (o1. 30s- 15) This invention relates to a piston and more particularly to a piston adapted for use in internal combustion motors and the principal object of the invention is to provide such a piston in which compression yis insured by an expansible skirt having an upper flange arranged in an annular groovein the l piston head, the clearance between the groove and flange being that customarily provided for piston rings. The invenl0 tion is capable of use`with or without piston rings.

One of the principal objectsof the invention is to provide such a piston in which the skirt is so anchored in the piston head that it can float and move freely therein so as to readily adapt itself to the piston walls and in which the skirt is of uniform symmetrical form throughout, containing no masses'of metal which would result in uneven expansion.

Another object of the present invention is to provide such a piston in which the skirt can be convenientlyremoved, the head being made, for this purpose, of two separate pieces separating along the line of. the plane of the groove so that by separating the sections the skirt can be conveniently withdrawn.

Another object of the present invention is to provide such a skirt having an inwardly projecting flange at its upper end which is split at one side and in which an L-shaped recess is also provided on the outside of the piston at the upper end of the split, this recess receiving an L-shaped cover which extends along the upper part of the split and thereby avoids the danger of Y leakage through the split.

Another object of the present invention is to so construct the piston that the skirt may be removed and inserted from the top of the cylinder by the simple expedient of removing the upper section of the piston head and withdrawing'the skirt.

Another purpose of the present invention is to provide means for preventing the skirt from turning relative to the piston head, except to a limited extent, by providingnal screw in the piston head which extends through a hole provided in the upper flange of the skirt.

In the accompanying drawing:

Fig. 1 is a side elevation of a piston embodying my invention.

Fig. 2 is a vertical transverse sectional view therethrough.

Fig. 3 is a top elevation thereof, showing the g same partly broken away.

Fig. 4 is a vertical sectional view taken on line #-4, Fig.` 2.

Fig. 5 is a bottom view.

Fig. 6 is a vertical sectional view through the upper section of a modified form of piston head, 5 in which a piston ring is provided.

The piston head, shown in Figs. 1-5, is composed of a lower disk-shaped portion III which is of less -diameter than the inside diameter of the skirt II so that the skirt II can be conveniently l0 removed by lifting it free from the disk-shaped part I0. This excess size of the piston skirt II also permits the piston skirt to yield inwardly or breathe in traversing the cylinder wall, as hereinafter described. The lower section I0 of 15 the piston head has the usual depending arms I2 which at their lower ends carry the Wrist pin I3. The arms I2 are preferably reenforced by ribs I4 in any usual and well known manner.

The disk-shaped section I0 is provided with a 20 threaded stud I5 and to this stud is secured the upper disk-shaped section I6 of the piston, this upper disk-shaped portion I6 having a neck or boss I1 which provides an annular groove I8 between the two sections.

'I'he skirt II is of cylindrical form and is formed at its upper end to provide an inwardly projecting annular flange I9 which is disposed within the groove I8. The clearance between the top and bottom of the flange I9 and the 30 annular groove I8 is preferably about .015 of an inch so that while the flange is positively held in the groove an oil seal is provided in the same manner as with piston rings. It will be seen that the skirt floats in the groove I8 so that it is free 35 to move and yield in adapting itself to the cylinder walls. It will also be seen that the skirt has no concentrated masses of metal, such as bosses for the wrist pin, etc. By eliminating such concentrated masses of metal, there is no tend- 40 ency to unevenness in expansion with resultant warping of the skirt. v

The skirt I I is split along one side, as indicated at 2li, this split permitting the skirt to adapt itself to the size of the cylinder both initially and 46 as'the cylinder and skirt wears. This split ex-` tends through the cylindrical side of the skirt and also through the upper flange I9, preferably extending through the upper flange I9 radially, as indicated by dotted lines in Fig. 3, and preferably extending obliquely down the side of the skirt, as indicated in Fig. 1, so as to avoid the dangerof scoring the cylinder wall. It is apparent that the flange 23 of the skirt is rmly held in the groove I8 and at the same time the skirt is entirely free to yield inwardly and 'outwardly, having in the nature of a floating connection to the piston head, this connection thereby securely holding the skirt and at the same time permitting it to yield and adapt itself to the cylinder walls. i

In order ,to hold the skirt il against turning l relative to the head a screw 2| is provided. This screw preferably has its head countersunk in a recess 22 in the upper piston head section I 6 and its threaded stem extends through a hole provided in the upper ange I9 of the skirt and into a threaded hole provided in the lower section I of the piston head. It is apparent that this screw not only prevents the skirt from turning.-

butalso locks the upper and lower sections I0 `and |6ofvthe head against turning relatively to one another so as to prevent these sections from erably stops short of the bottom of the piston.

In the grooves 23 and 24 is arranged an L-shaped cover 25, the upper part of which ts into the groove 23 and the side part of which ts the groove 24. 'I'his cover is made so that when inserted it forms a continuation of the outer Wall of the skirt and serves to prevent leakage through the upper part of the split 20. A slight clearance of approximately .015 of an inch is left between the edges of this cover and the grooves 23 and 24 so as to provide an oil seal.

In assembling thepiston the skirt isplaced over the disk l0, the L-shaped cover 25 is placed in the grooves 23 and 24 and the upper section I6 of`the head is then screwed down. The screw 2| is then inserted and the skirt is held against turning relative to the piston head and at the same time the two sections of the piston head are locked together. With this construction itis apparent that after the piston has been placed in the cylinder the skirt can be replaced by removing the cylinder head, removing the screw 2l, unscrewing the upper section I6 of the piston head and lifting the skirt Il out of the cylinder and replacing it with another one. It is also apparent that by the provision of the ange I9 closely held within the groove I8 with only enough clearance to provide an oil seal that the skirt is positively held in the head but is f ree to float therein and expand or contract to adapt itself to the cylinder walls. It is also apparent that there is no danger of leakage past the skirt particularly with the provision of the cover 24 which provides a seal around the upper part of the split through the skirt.

In Fig. 6 is illustrated a modied form ofthe upper section lGa of the piston head, this being generally similar to the piston head section I6 shown in the form of the invention illustrated in Figs. 1-5, except that it is additionallyprovided with a piston ring groove 30 in which'a conventional piston ring 3l is placed. The other parts of the piston head section I6a are substantially identical with the piston head section I 6 and therefore the same reference numerals have been employed and distinguished by the suflix da". the piston ring 3| further guards against leakage past the piston, the piston additionally having the advantages obtained by the provision of the iioating skirt which has no concentrated masses of metal.

I claim as my invention:

1. A piston, comprising a lower head section, an upper head section, screw means connecting said head sections, said head sections when tightly connected providing between them an annular, peripheral groove of substantial depth which is closed at its inner end, a skirt tting around said head and having an inwardly projecting annular ange slidingly and closely fitted in said groove, and a pin extending through one head section and skirt and into the other head section and restricting relative movement of said head and skirt and also preventing said head sections from unscrewing.

2. A piston, comprising a head, a skirt surrounding said hea'd and having at one end an inwardly projecting annular flange engaging said head, said skirt and iiange being provided with acontinuous L-shaped split extending from one edge of said flange to the opposite edge of said skirt, means for securing said skirt to said head, the outer side of said ange being recessed around said split and said external recess extending along the side of said skirt around said split and an L-shaped cover in said recess and sealing the upper end of said split.

3. A piston, comprising a head having an annular peripheral groove, a skirt tting around said head and having at one end an inwardly projecting annular ange yieldingly and closely tted in said groove, said end flange being provided with a continuous L-shaped split extending from one edge of said flange to the opposite edge of said skirt, the outer side of. said ange being recessed around said split and this recess being extended along `the outside of said skirt around said split, and an L-shaped cover in said recess and sealingA the .upper end of said split.

4. A piston, comprising a lower head section, an upper head section, screw means connecting said head sections, said head sections when tightly connected providing between them an annular,

peripheral groove of substantial depth, a skirt.

tting around said head and having an inwardly projecting annular flange at one end closely tted in said groove, said skirt and flange being provided with a continuous L-shaped split extending from one edge of said flange to the opposite edge of said skirt, the outer side of said flange being recessed around said split and this recess being extended along the outside of said skirt and said split andan L-shaped cover in said recess and sealing the upper end of said skirt.

LEON A. HALLSTEAD.

It will be appreciated that the provision ofl 

